I think this is B. ruderatus (photogtaphed last year near my home in Madrid)

Look at the thorax - a clear yello/orange band at the top and bottom - and a yellow band at the top of the abdomen. The white section at the bottom is just visible in this photo bute was clearer in others taken at the same time.

Thanks for your help, Alan. Your black and orange specimen makes my id look way out. All black or nearly all black bumble bees are a problem for me as it looks as though they could be one of several species. My thought that it might be ruderatus was more hope than judgement as I am surveying bees (and all insects at Carymoor nature reserve in east Somerset) in the hope of securing funding to protect BAP protected species. The specimen was larger than any other bee I saw that day. Many thanks for your help. All the best, Jules